The present invention relates to a new and improved apparatus to allow the remote actuation of an elevator traction drive sheave to permit manual control of an elevator car in the event of an emergency.
Conventional elevator systems typically include a motor installation having a motor-operated transmission which raises and lowers one or more cables to which the elevator car is affixed. In the event of an emergency condition, a friction brake is automatically engaged which bears against a rotating element of the transmission, such as a main cable sheave, and locks the sheave in position, preventing further cable and thus elevator car motion. While such devices provide a positive and effective stop against car motion, it is often difficult to release the brake in a controlled manner and under controlled conditions to allow the cab to be manually raised or lowered, such as for evacuation purposes.
U.S. Pat. No. 5,680,911 discloses an elevator emergency release device in the form of a pull cable which pivots an application rod, causing engagement of a manually-operated gear unit to mesh with a corresponding gear of the elevator transmission. At the same time, the motion of the application rod causes the disengagement of the previously-applied emergency brake. Subsequent manual operation of a second cable causes the manual rotation of the transmission spindle, allowing the elevator car to be raised or lowered as required. Such a device requires the manual operation of both cables, both of which are typically located outside the elevator car. The presence of multiple cables make it inconvenient or difficult to operate, particularly when a car occupant is faced with an emergency situation. Further, the requirement that the actuating cables be operated by a car occupant reaching outside the car with both arms can be disconcerting.
It is accordingly a purpose of the present invention to provide an emergency elevator manual drive unit which is operable through a single control mechanism.
A further purpose of the present invention is to provide a device for manually releasing an elevator drive brake and subsequently moving the elevator which can be employed for use either by a car occupant or by personnel at the elevator hoistway.
Yet a further purpose of the present invention is to provide a device for the failsafe manual operation of an elevator, such as in emergency conditions, by which a single, hand-operated unit both releases the emergency brake and allows for the raising or lowering of the elevator car in a safe and controlled manner.
In accordance with the foregoing and other objects and purposes, an emergency manual elevator drive device constructed in accordance with the present invention comprises a friction brake adapted for engagement with a rotating member of an elevator transmission in an emergency situation in a manner known in the art. A linkage element is pivotally mounted to the, brake and supports a manually-operable drive roller. Means are provided for applying a force to the linkage element to allow the drive roller to be pivoted into contact with the elevator drive member when the drive member is braked by the friction brake during an emergency condition, and to pivot the friction brake away from the drive member once the drive roller is in contact with the drive member, allowing the drive member to be rotated by the manual drive roller to raise or lower the car.
In a preferred embodiment the force is applied to the linkage element through a pulley or gear having a drag bushing by which the drive roller is mounted to the linkage element. Rotational force is applied to the drive roller through a drive belt, rope or chain driven by a hand crank, located for example at the elevator car. The drag bushing causes a force imbalance to be generated in the chain and applied to the linkage element, causing pivoting of the linkage arm first about the brake pivot point to engage the drive roller with the drive member and thereafter, when the drive roller is engaged with the drive member to pivot, about the drag bushing and drive roller to back the brake away from the drive member. With the friction brake partially disengaged from the drive member, the manual drive roller remains in engagement with the drive member, turns the drive member, and allows the elevator car to be moved in a controlled manner.
The system is self-regulating, as the force imbalance applied by the belt or chain cannot exceed that which is required to back the brake from the drive member only enough to allow the drive member to be driven by the manual drive roller and a dynamic equilibrium to be established. Continued manual operation of the crank is required to maintain the equilibrium. Any release of the crank removes the applied force imbalance and causes the brake to return to its normal engaged position, stopping motion of the drive member and the elevator car, and disengages the manual drive roller from the drive member.